Organ keyboards originally had only the long keys (the white keys) because they only had the natural notes of the scale. The accidentals were added later as the short keys, and were added as short keys so you could still play as though they weren't there.
Piano keys are the same because they copied the keyboard from the harpsichord, which copied it from the organ.
The reason the long keys are in C is because a piano is naturally tuned to C. Tighten all the strings a bit to bring it up to D, and all the long keys will be in the key of D.
... briefly, before the piano implodes.
If you're asking "why is it tuned to C", it's probably because C is the key that historically was assigned the letters without any sharps or flats. There's no physical reason for this, it's just a convention (as opposed to, say, octaves, where each octave is half the frequency of the previous).
If you're asking why C got the letters without sharps or flats, I believe you have the Romans to blame for that. They did start with A for their scale without sharps or flats, but it was what we would now call "A minor". Which leaves C as the major scale.
Doesn't that seem really stupid to you now or do you still support that stance? Refusing to learn the entire field of music because of one irrelevant detail is pretty appalling.
Similar logic puts some people off of Christianity - x is in the Bible, and we know the Bible is true because the Bible says it is true, therefore x is also true. Hmm. Someone who tries to sell you that logic is also either lying or wrong, now you can't trust either that person or the Bible.
There's a huge difference between "it's not worth our time to resolve this now" and "non-rigorous thought is okay, reality doesn't have to make sense, just do what the high-status people say, they're smarter".
[1] There's a practice in some groups to explicitly say "it works by magic" to avoid false understandings and to flag unresolved issues.
Yes, exactly.
I had a similar experience with music instruction, everyone taught to the instrument and to the book of music, never any concepts of music theory even to the point of "What's with the sharps and flats over here by the squiggle? Why not put them where I can see them easier?" "Yeah, I don't know, it's kind of a pain, I just write them back in with pencil." "How do you write a new song?" "Oh, it's really hard, you have to be really smart like Beethoven. Don't worry about that, we have plenty of stuff to practice in the book."
Later, in self educating, I discovered key signatures, playing to those keys (and even improvising!), and that I don't have to think about sharps and flats except for accidentals and it makes so much goddamn sense, but no adult I had access to in childhood ever knew or at least none could explain something which was so fundamental, something that actually made music fun and allowed me to create a positive-feedback loop required for consistent practice.
Had I stood firmer on the grandparent's question, rejected instruction sooner (instead of just through confused burn-out), and begun to self educate sooner, I could have avoided wasting a lot of time.
My partner is quite musical though (formally trained), and she's help fill in a lot of the gaps. I'm at the point now where I can fiddle around with different chord progressions and get good-sounding melodies to come out on my own. I get inversions and how they work on the guitar, etc. It's quite cool and way more interesting to me than just learning songs from a book.
Unless your parents are directing you, childhood is a random walk through the universe of creative possibility.
(The correct answer is that people's hands aren't wide enough to deal with all twelve notes on the same level, and that particular subset of the notes contains a lot of consonant intervals and barely any dissonant ones.)